MODULATION OF FATTY ACIDS IN THE MEMBRANES OF ANACYSTIS NIDULANS (CYANOBACTERIA): INCORPORATION OF ODD-NUMBERED CARBON FATTY ACIDS1

Anacystis nidulans Richt., a unicellular cyanobacterium, can incorporate exogenously supplied fatty acids, including odd-numbered carbon fatty acid (OFAs), into the acylglycerols of cell membranes. Data are presented for the uptake of undecanoic acid (11:0) into cells of A. nidulans, the subsequent elongation up to C17, and incorporation of OFA into the four major membrane acylglycerols. The incorporation of OFAs was followed by desaturation of part of the saturated fatty acid to monoenoic fatty acid. Positional analyses of the double bonds of these manoenoic fatty acids suggest that there is one desaturase that inserts a Δ⁹ bond in both odd- and even-numbered fatty acids of varying chain length. Our data also suggest that there is no positional specificity for chain length on the glycerol backbone by the acyltransferases.     

Methylmalonic and propionic acidemias: lipid profiles of normal and affected human skin fibroblasts incubated with [1-14C]propionate

Normal human skin fibroblasts and those from methylmalonic acidemia and propionic acidemia patients were grown in culture. Following incubation with [1-14C]propionate, the major lipid classes in the cells were separated by thin layer chromatography and isolated fractions analyzed by radio gas chromatography for the presence of odd-numbered long-chain fatty acids; the pattern of even-numbered long-chain fatty acids was obtained also. Normal fibroblasts incorporated a small percentage of propionate into odd-numbered fatty acids which were present in all lipids studied. The abnormal cells incorporated a larger amount while maintaining the characteristic ratios of odd-numbered fatty acids found in the normal line. Most of the radioactivity was associated with phospholipids which are the predominant constituents of cell membranes. A characteristic C15/C17 ratio was found for different phospholipids and the triglyceride fraction; pentadecanoic acid was the principal odd-numbered fatty acid utilized in the assembly of complex lipids. Compared to even-numbered long-chain fatty acids the absolute amount of odd-numbered fatty acids was low (1-2%), even in affected cells. An unusual polar lipid fraction was isolated in the course of the study. In the normal cell it contained several unlabeled eicosanoids which were missing from the same fraction of both affected cell lines.     

Further evidence for an elongation-decarboxylation mechanism in the biosynthesis of paraffins in leaves

In isolated tobacco leaves l-valine-U-¹⁴C gave rise to labeled even-numbered isobranched fatty acids containing 16 to 26 carbon atoms and iso C₂₉, iso C₃₁, and iso C₃₃ paraffins. l-Isoleucine-U-¹⁴C on the other hand produced labeled odd-numbered anteiso C₁₇ to C₂₇ fatty acids and anteiso C₃₀ and C₃₂ paraffins. Trichloroacetic acid inhibited the incorporation of isobutyrate into C₂₀ and higher fatty acids and paraffins without affecting the synthesis of the C₁₆ and C₁₈ fatty acids. Thus the very long branched fatty acids are biosynthetically related to the paraffins. In Senecio odoris leaves acetate-1-¹⁴C was incorporated into the paraffins (mainly n-C₃₁) only in the epidermis although acetate was readily incorporated into fatty acids in the mesophyll tissue. Similarly only the epidermal tissue incorporated acetate into fatty acids longer than C₁₈ suggesting that the epidermis is the site of synthesis of both paraffins and the very long fatty acids. In broccoli leaves n-C₁₂ acid labeled with ¹⁴C in the carboxyl carbon and ³H in the methylene carbons was incorporated into C₂₉ paraffin without the loss of ¹⁴C relative to ³H. Since n-C₁₈ acid is known to be incorporated into the paraffin without loss of carboxyl carbon these results suggest that the condensation of C₁₂ acid with C₁₈ acid is not responsible for n-C₂₉ paraffin synthesis in this tissue. Thus all the experimental evidence thus far obtained strongly suggests that elongation of fatty acids followed by decarboxylation is the most likely pathway for paraffin biosynthesis in leaves.     

Tests Whether a Head to Head Condensation Mechanism Occurs in the Biosynthesis of n-Hentriacontane, the Paraffin of Spinach and Pea Leaves

Isobutyrate-1-¹⁴C and l-isoleucine-U-¹⁴C fed through the petiole labeled the surface lipids of broccoli leaves, but the incorporation was much less than from straight chain precursors. Not more than one-third of the ¹⁴C incorporated into the surface lipids was found in the C₂₉ paraffin and derivatives, whereas more than two-thirds of the ¹⁴C from straight chain precursors are usually found in these compounds. The small amount of ¹⁴C incorporated into the paraffin fraction was found in the n-C₂₉ paraffin rather than branched paraffins showing that the ¹⁴C in the paraffin must have come from degradation products. Radio gas-liquid chromatography of the saturated fatty acids showed that, in addition to the n-C₁₆ acid which was formed from both branched precursors, isoleucine-U-¹⁴C gave rise to branched C₁₅, C₁₇, and C₁₉ fatty acids, and isobutyrate-1-¹⁴C gave rise to branched C₁₆ and C₁₈ acids. Thus the reason for the failure of broccoli leaf to incorporate branched precursors into branched paraffins is not the unavailability of branched fatty acids, but the absolute specificity of the system that synthesizes paraffins, probably the elongation-decar-boxylation enzyme complex. Consistent with this view, no labeled branched fatty acids longer than C₁₉ could be found in the broccoli leaf. The branched fatty acids were also found in the surface lipids indicating that the epidermal layer of cells did have access to branched chains. Thus the paraffin synthesizing enzyme system is specific for straight chains in broccoli, but the fatty acid synthetase is not.     

Waxmonoester fermentation in Euglena gracilis T. Factors favouring the synthesis of odd-numbered fatty acids and alcohols

Waxmonoester fermentation at the expense of endogenous paramylon was followed in the dark in autotrophically grown Euglena gracilis. With reduced oxygen tension and decreasing O₂-consumption rates the proportion of odd-numbered fatty acids and alcohols increased up to a molar ratio of nearly 1:1 under strictly anaerobic conditions. Labelled ¹⁴CO₂, succinate and propionate were incorporated into odd-numbered fatty acids and alcohols 11 to 33 times faster than in even-numbered chains. The electron-flow inhibitor rotenone diminished waxester formation in total, but especially CO₂ fixation and the synthesis of odd-numbered chains, without impeding anaerobic carbohydrate breakdown. These findings are indicative for propionyl-CoA as an intermediate in the synthesis of odd-numbered chains. Its probable synthesis in the methylmalonyl-CoA pathway is discussed with regard to energetics.Abbreviation CCCP carbonylcyanide m-chlorophenyl hydrazone     

Effect of Ethrel and Ceratocystis fimbriata on the Synthesis of Fatty Acids and 6-Methoxy Mellein in Carrot Root

The rate of incorporation of ¹⁴C from acetate-1-¹⁴C into fatty acids by carrot root discs, 18 hours after inoculation with Ceratocystis fimbriata, was 9-fold greater than that in freshly cut discs. The rate in discs treated with water or Ethrel was 3-fold greater. The rate of incorporation of ¹⁴C from glucose-U-¹³C into fatty acids was 3-fold greater 18 hours after any of the above treatments. The rate of ¹⁴C incorporation from malonate-2-¹⁴C into fatty acids 24 hours after inoculation with C. fimbriata or treatment with water was 25 and 60%, respectively, of that in freshly cut discs. Linoleic acid was the principal fatty acid in carrot root, but incorporation of ¹⁴C from acetate-1-¹⁴C into the acid was low until 18 hours after inoculation with C. fimbriata or treatment with Ethrel. Turnover rates of the fatty acids appeared low and were similar for all treatments.     

Substrate utilization for energy production and lipid synthesis in oligodendrocyte-enriched cultures prepared from rat brain

The metabolism of oligodendrocytes has been studied using cultures of oligodendrocyte-enriched glial cells isolated from cerebra of 5–8-day old rats. Cultures containing 60–80% oligodendrocytes were incubated for 16h with [3-¹⁴C]acetoacetate, d-[3-¹⁴C]3-hydroxybutyrate, [U-¹⁴C]glucose, l-[U-¹⁴C]glutamine and [1-¹⁴C]pyruvate or [2-¹⁴C]pyruvate in the presence or absence of other oxidizable substrates. Labelled CO₂ was collected as an index of oxidative metabolism and the incorporation of label into total lipids, fatty acids and cholesterol was used as an index of the de novo synthesis of lipids. Glucose, acetoacetate, D-3-hydroxybutyrate, pyruvate and l-lactate were measured to determine substrate utilization and product formation under various conditions. Our results indicate that glucose is rapidly converted to lactate and is a relatively poor substrate for oxidative metabolism and lipid synthesis. Ketone bodies were used as an energy source and as precursors for the synthesis of fatty acids and cholesterol. Preferential incorporation of acetoacetate into cholesterol was not observed. Exogenous pyruvate was incorporated into both the glycerol skeleton of complex lipids and into cholesterol and fatty acids. l-Glutamine appeared to be an important substrate for the energy metabolism of these cells.     

Odd-and even-numbered fatty acids. Their contrasting behavior in normal and fowlpox virus-infected epithelium.

Upon infection with fowlpox virus, the amount of odd-numbered fatty acids in chick scalp epithelium shows a significant decrease compared with control values. This effect begins quite early and progresses throughout the period of infection. Individual members of the odd-numbered family (C15--C27 inclusive) were quantitatively related to the group as a whole during most of the infection. Experiments involving the administration of labeled acetate in vivo demonstrated an increase in the synthesis of even-numbered fatty acids and a decrease in the synthesis of odd-numbered fatty acids in infected epithelium. The reduced synthesis of odd-numbered fatty acids in infected epithelium could also be demonstrated with labeled propionate. The influence of the alpha-oxidation pathway was assayed in chick scalp epithelium in vivo by the administration of [1-14C,9,10-3H] stearic acid. The C17 acids formed had a 3H/14C ratio similar to that of the C16 acids, indicating that most label incorporation into C17 was due to beta-oxidation to acetate followed by resynthesis into fatty acids. C17 fatty acids from control and infected epithelium had similar 3H/14C ratios, indicating that the alpha-oxidation pathway probably does not contribute to the differences in odd-numbered fatty acid content observed. In assays for fatty acid synthetase activty, both [14C] acetyl-CoA and [14C]-propionyl-CoA were used as initial acceptors. The specific activities of preparations from infected scalp were similar to those of control preparations with both substrates. These results suggest that there is no decline in the ability to utilize propionate for fatty acid synthesis in infected epithelium.     

Importance of 3-Hydroxy Fatty Acid Composition of Lipopeptides for Biosurfactant Activity

Biosurfactant production may be an economic approach to improving oil recovery. To obtain candidates most suitable for oil recovery, 207 strains, mostly belonging to the genus Bacillus, were tested for growth and biosurfactant production in medium with 5% NaCl under aerobic and anaerobic conditions. All strains grew aerobically with 5% NaCl, and 147 strains produced a biosurfactant. Thirty-five strains grew anaerobically with 5% NaCl, and two produced a biosurfactant. In order to relate structural differences to activity, eight lipopeptide biosurfactants with different specific activities produced by various Bacillus species were purified by a new protocol. The amino acid compositions of the eight lipopeptides were the same (Glu/Gln:Asp/Asn:Val:Leu, 1:1:1:4), but the fatty acid compositions differed. Multiple regression analysis showed that the specific biosurfactant activity depended on the ratios of both iso to normal even-numbered fatty acids and anteiso to iso odd-numbered fatty acids. A multiple regression model accurately predicted the specific biosurfactant activities of four newly purified biosurfactants (r² = 0.91). The fatty acid composition of the biosurfactant produced by Bacillus subtilis subsp. subtilis strain T89-42 was altered by the addition of branched-chain amino acids to the growth medium. The specific activities of biosurfactants produced in cultures with different amino acid additions were accurately predicted by the multiple regression model derived from the fatty acid compositions (r² = 0.95). Our work shows that many strains of Bacillus mojavensis and Bacillus subtilis produce biosurfactants and that the fatty acid composition is important for biosurfactant activity.     

THE INCORPORATION OF [1-14C]ACETATE INTO UNESTERIFIED FATTY ACIDS IN RAT CEREBRAL CORTEX IN VIVO

—The incorporation of [1-¹⁴C]acetate into unesterified fatty acids and into the fatty acids of neutral glycerides and of phospholipids has been measured in rat cerebral cortex in vivo. The most rapid incorporation is seen in the unesterified fatty acids which have a turnover time of 5-6 min. It is suggested that unesterified fatty acids are precursors to neutral glycerides and phospholipids rather than being derived from them by lipase activity.     

In vitro synthesis of mycolic acids by the fluffy layer fraction of Bacterionema matruchotii

Biosynthetic activity for mycolic acid occurred in the fluffy layer fraction but not in the 5000g supernatant of Bacterionema matruchotii. With [1-¹⁴C]palmitic acid as precursor for the in vitro system, the predominant product was identified as C_32:0 mycolic acid by radio-gas-liquid chromatographie (radio-GLC) and gas chromatographic/mass spectroscopic analyses; if [1-¹⁴C]stearic acid was used, two major radioactive peaks appeared on GLC: one corresponding to the peak of (C_34:0 + C_34:1) mycolic acids and the other to (C_36:0 + C_36:1) mycolic acids. By pyrolysis/radio-GLC analysis, C_32:0 mycolic acid synthesized by [1-¹⁴C]palmitic acid was pyrolyzed at 300 °C to form palmitaldehyde (the mero moiety) and methyl palmitate (the branch moiety). The pH optimum for the incorporation of [1-¹⁴C]palmitate into bacterionema mycolic acids was 6.4 and the reaction required a divalent cation. The in vitro system utilized myristic, palmitic, stearic and oleic acids (probably via their activated forms) well as precursors, among which myristic and palmitic acids were more effective than the rest. Avidin showed no effect on the biosynthesis of mycolic acid from ¹⁴C-palmitate whereas cerulenin, a specific inhibitor of β-ketoacyl synthetase in de novo fatty acid synthesis, inhibited the reaction at a relatively higher concentration. Thin-layer chromatographic analysis of lipids extracted from the reacting mixture without alkaline hydrolysis showed that both exogenous [1-¹⁴] fatty acid and synthesized mycolic acids were bound to an unknown compound by an alkali-labile linkage and this association seemed to occur prior to the condensation of two molecules of fatty acid.     

Elongation Pathway for alpha-Linolenic Acid Synthesis in Spinach Leaves: A Reexamination

Leaf slices from spinach exhibited considerable variation in their incorporation of [¹⁴C]bicarbonate and [1-¹⁴C]acetate into fatty acids. Reductive ozonolysis studies indicated that all the ¹⁴C-labeled fatty acids were synthesized de novo; no in vivo evidence was found for the previously proposed elongation of hexadecatrienoate to α-linolenate.     

In vivo labeling of myelin lipids and proteolipid protein with [3H]myristate, [14C]linoleate,and [14C]linolenate

To investigate the incorporation of essential fatty acids into myelin components, 24-day-old rabbits were injected intracerebrally with [¹⁴C]linoleate, [¹⁴C]linolenate, or [³H]Myristate for comparison. Animals were killed 22 hr later and myelin was isolated. [³H]myristate labeled all myelin lipids including monogalactosyl diglyceride, with the exception of sulfatides. With¹⁴C-essential fatty acids, only glycerophospholipids were efficiently labeled and their specific activities were in the following decreasing orders: PC>PI>PE>PS with [¹⁴C]linoleate, and PE>PC>PI=PS with [¹⁴C]linolenate. Among myelin proteins, PLP and DM-20 were labeled with all 3 precursors. PLP was purified from myelin labeled with¹⁴C-essential fatty acids. The label was then cleaved from the protein by alkaline methanolysis and was identified as a dienoic ([¹⁴C]linoleate) or a tetraenoic ([¹⁴C]linolenate) fatty acid. MBP was not labeled with [³H]myristate, but was slightly labeled with both¹⁴C-essential fatty acids. The signification of the latter result is discussed.Abbreviations FA fatty acid(s) - HPTLC high-performance thin-layer chromatography - MBP myelin basic protein - PLP proteolipid protein - PC phosphatidylcholine - PE phosphatidylethanolamine and ethanolamine plasmalogens - PI phosphatidylinositol - PS phosphatidylserine - SDS sodium dodecylsulfate     

Plasmodium lophurae: Quantitative in vitro incorporation of 14C-1-acetate into lipids

Blood from ducks parasitized with Plasmodium lophurae and normal duck blood were incubated with sodium ¹⁴C-1-acetate. After release of the parasites from infected red blood cells (RBC) and concurrent treatment of normal blood, lipids were extracted from cellular material and plasma and lipid classes separated by thin-layer chromatography. Specific activity (dpm/mg lipid) of lipid classes was measured quantitatively by liquid scintillation radioassay and gravimetric analysis. The data indicated that the parasite within the RBC incorporated ¹⁴C-labeled lipid precursors.Experiments employing sodium ¹⁴C-1-acetate in two concentrations, 50 μCi ¹⁴C in 0.91 μmole sodium acetate/50 ml blood and 500 μCi ¹⁴C in 9.1 μmole sodium acetate/50 ml blood (1.82 × 10^?5M and 1.82 × 10^?4M), showed higher ¹⁴C incorporation into parasitized blood than normal blood preparations at the higher substrate concentration at 5 hr of incubation. At $\text{1.82 × 10}{}^{\mathrm{?5}}\text{M}{}^{14}$C-1-acetate, the highest specific activity in P. lophurae was associated with lipid alcohols. Monoglycerides and diglycerides were significantly labeled. At the higher acetate concentration (1.82 × 10^?4M), monoglyceride and diglyceride lipid classes had the highest specific activity in preparations of partially purified P. lophurae.Lipids of plasma from parasitized blood incubated for 5 hr with both concentrations of labeled acetate exhibited the highest specific activity in the free fatty acid class and sterols.At 24 hr of incubation, the lipids of partially purified P. lophurae had increased specific activity in free fatty acids, diglycerides, monoglycerides, phospholipids, and triglycerides.In plasma from parasitized blood incubated 24 hr with ¹⁴C-1-acetate, the highest specific activity and greatest percent of ¹⁴C incorporation was found in free fatty acids.     

Fatty acids in the genus Bacillus. II. Similarity in the fatty acid compositions of Bacillus thuringiensis, Bacillus anthracis, and Bacillus cereus

The nature and relative abundance of fatty acids produced by two strains each of Bacillus thuringiensis and of B. anthracis were studied by gas-liquid chromatography on a 12,000 theoretical plate polyester column capable of partially resolving iso- and anteiso-fatty acids with the same number of carbon atoms. Unsaturated fatty acids as the bromo derivatives were separated from the saturated acids and resolved in a short SE-30 column by use of programmed-temperature gas chromatography. All four strains produced 16 major fatty acids: 9 branched (i-C₁₂, i-C₁₃, i-C₁₄, i-C₁₅, i-C₁₆, i-C₁₇, a-C₁₃, a-C₁₅, and a-C₁₇), 3 normal (n-C₁₄, n-C₁₅, and n-C₁₆), and 4 monounsaturated (i-C₁₆¹⁼, i-C₁₇¹⁼, a-C₁₇¹⁼, and n-C₁₆¹⁼), in addition to some minor fatty acids. In all cases, 12 branched acids, including saturated and monounsaturated, made up over 70% of the total fatty acids, and iso-C₁₅ acid was most abundant. These fatty acid distribution patterns were very similar to those of B. cereus and B. cereus var. mycoides. There were, however, minor but clear differences between the fatty acid distribution patterns of B. thuringiensis and B. anthracis. B. thuringiensis, like B. cereus, produced higher proportions of i-C₁₃, a-C₁₃, and i-C₁₄ fatty acids than did B. anthracis. This difference between these two species could be useful as a supplemental criterion in their differentiation. Indications are that the enzyme systems for monounsaturated fatty acid synthesis in B. thuringiensis and B. anthracis prefer normal fatty acids as substrates rather than branched-chain fatty acids.     

The biosynthesis of the hydrocarbons in males and females of the millipede Graphidostreptus tumuliporus

The in vivo hydrocarbon biosynthesis in the millipede Graphidostreptus tumuliporus was studied after the injection of 1-¹⁴C-acetate, 16-¹⁴C-, and 1-¹⁴C-palmitic acid.From all precursors used an active incorporation into the unsaturated hyrocarbons (alk-1-enes, alkadienes, and alkatrienes) was observed, whereas no radioactivity was incorporated into the saturated alkanes at all, in accordance with their supposed exogenous origin (food). From the distribution of the radiolabel over both the various hydrocarbon classes and the individual hydrocarbon components it was concluded that in this millipede hydrocarbons are synthesized from fatty acids (irrespective of their chain structure) by an elongation-decarboxylation mechanism in which an α-oxidation step is involved, whilst during the decarboxylation process a terminal double bond is introduced. Thus, saturated fatty acids give rise to alk-1-enes (as is evidenced by an overwhelming incorporation of palmitic acid into the alk-1-enes), monoenoic fatty acids to alkadienes, and dienoic fatty acids to alkatrienes.The proposed mechanism for hydrocarbon biosynthesis in G. tumuliporus has not yet been described in other organisms.     

Control of plastidic glycolipid synthesis and its relation to chlorophyll formation

Mechanisms restricting the accumulation of chloroplast glycolipids in achlorophyllous etiolated or heat-treated 70S ribosome-deficient rye leaves (Secale cereale L. cv “Halo”) and thereby coupling glycolipid formation to the availability of chlorophyll, were investigated by comparing [¹⁴C]acetate incorporation by leaf segments of different age and subsequent chase experiments. In green leaves [¹⁴C]acetate incorporation into all major glycerolipids increased with age. In etiolated leaves glycerolipid synthesis developed much more slowly. In light-grown, heat-bleached leaves [¹⁴C]acetate incorporation into glycolipids was high at the youngest stage but declined with age. In green leaves [¹⁴C]acetate incorporation into unesterified fatty acids and all major glycerolipids was immediately and strongly diminished after application of an inhibitor of chlorophyll synthesis, 4,6-dioxoheptanoic acid. The turnover of glyco- or phospholipids did not differ markedly in green, etiolated, or heat-bleached leaves. The total capacity of isolated ribosome-deficient plastids for fatty acid synthesis was not much lower than that of isolated chloroplasts. However, the main products synthesized from [¹⁴C]acetate by chloroplasts were unesterified fatty acids, phosphatidic acid, and diacylglycerol, while those produced by ribosome-deficient plastids were unesterified fatty acids, phosphatidic acid, and phosphatidylglycerol. Isolated heat-bleached plastids exhibited a strikingly lower galactosyltransferase activity than chloroplasts, suggesting that this reaction was rate-limiting, and lacked phosphatidate phosphatase activity.     

The sensitivity of acetyl-coenzyme A carboxylase to citrate stimulation in a homogenate of rat liver containing subcellular particles

1. Although citrate is known to activate purified preparations of acetyl-CoA carboxylase, it had no stimulatory effect on the incorporation of [¹⁴C]acetate into long-chain fatty acids in a whole homogenate of rat liver (S_0.7) under conditions in which the activity of acetyl-CoA carboxylase was rate-limiting for fatty acid synthesis. 2. The rate of incorporation of acetyl carbon into fatty acids was estimated in S_0.7 preparations incubated with [¹⁴C]acetate, by measuring the specific radioactivity of the acetyl carbon of acetyl-CoA and the incorporation of ¹⁴C into fatty acids. These estimates were compared with estimates of acetyl-CoA carboxylase activity in the S_0.7 preparation obtained by direct assay in conditions in which the enzyme was in the fully activated state. 3. In the absence of citrate, incorporation of acetyl carbon into fatty acids was about 75% of the value expected if the acetyl-CoA carboxylase in the S_0.7 preparation were in the fully activated state. 4. Incorporation of acetyl carbon into fatty acids in the S_0.7 preparation was stimulated by citrate, but the effect was many times less than the stimulation of [¹⁴C]acetate incorporation by citrate in particle-free preparations. 5. When the mitochondria and microsomes were removed from the S_0.7 preparation, [¹⁴C]acetate incorporation into fatty acids fell to a negligible value and the preparation became highly sensitive to stimulation by citrate. 6. It is suggested that in the presence of mitochondria and microsomes, and in the intact liver cell, the degree of activation of acetyl-CoA carboxylase is such that citrate activation may not be of physiological significance.     

Physiology of Sporeforming Bacteria Associated with Insects II. Lipids of Vegetative Cells

Lipid composition was studied in two strains each of mid-log phase cells of Bacillus thuringiensis, B. larvae, B. popilliae, B. alvei, and B. lentimorbus. Total lipids varied from 2.5 to 3.5% of the cell dry weight of B. thuringiensis to 4.3 to 5.0% of B. popilliae. Phospholipids in the organisms examined ranged from 55 to 79% of total lipids; neutral lipids averaged from 13 to 45%. Common phospholipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, and lysophosphatidylethanolamine. 1,2-Diglycerides, methyl esters, free fatty acids, and hydrocarbons were found in all the organisms studied. Branched-chain fatty acids constituted more than 50% of the total fatty acids in B. thuringiensis, B. larvae, B. popilliae, and B. alvei, whereas, in B. lentimorbus, normal-chain acids constituted more than 50%. Anteiso-C₁₅ (12-methyltetradeconoate) was the most abundant acid (30 to 50%) in B. alvei, B. larvae, B. popilliae, and B. lentimorbus. In contrast, B. thuringiensis contained more iso-C₁₃ (7%), iso-C₁₅ (17%), normal-C₁₆ (24%), and iso-C₁₇ (18%) than anteiso-C₁₅ (6%). The distribution of individual fatty acids was similar in the phospholipids and neutral lipids of each organism. However, the total amount of iso, anteiso, and normal isomers differed.     

Biosynthesis and metabolism of steryl glycosides in Sinapis alba seedlings

With ¹⁴CO₂, d-glucose-[U-¹⁴C] and dl-mevalonate-[4R-4-³H₁] used as precursors, a study was made of the labelling dynamics of the steryl glucosides (SG) and steryl acylglucosides (ASG) in Sinapis alba seedlings. The radioactivity of the sterol and sugar moieties, as well as of the fatty acid moieties in the case of ASG, was analysed separately. The course of incorporation of ¹⁴C from ¹⁴ CO₂ and glucose-[U-¹⁴C] into the sugar part of SG and ASG indicated that about $\text{2}\text{3}$ of the whole pool of the newly synthesized sterol glycosides of both types underwent rapid deglucosylation. Likewise, fatty acids in the ASG pool were rapidly exchanged. The present results point to a high metabolic activity of the sterol glycoside derivatives in plant cells.